1. Field of the Invention
The present invention relates to a method for drying wood, and more particularly to a method for drying green wood such as thinnings, green bamboo or similar other green plants in a short period of time. In the present specification, the term xe2x80x9cwoodxe2x80x9d includes the bamboo and other green plants.
2. Description of the Prior Art
Conventionally, there are proposed various methods for drying wood including a method in which green wood is put in a drying room to be sealed, and wood fuels such as waste wood are put into a combustion chamber provided in a lower area of a combustion gas generating furnace to be sealed and then the wood fuels are burned, followed by introducing a high-temperature combustion gas generated by the burning into an upper area of the drying room, to thereby dry the wood, wherein the concentration of the oxygen in the drying room is maintained to a low level.
According to the above-mentioned conventional method for drying wood, the wood can be dried safely and uniformly by maintaining the concentration of the oxygen in the drying room, i.e. the oxygen content in the combustion gas, to such a low level as being almost equal to zero. However, the above conventional method for drying wood by controlling the concentration of the oxygen is insufficient to efficiently dry the wood in a short period of time and is required to be further improved.
It is therefore an object of the present invention to provide a method for drying wood which is capable of efficiently drying the wood in a shorter period of time, by maintaining the concentration of the combustion gas for use in drying the wood to a high value and by maintaining the pressure of the drying room atmosphere containing the combustion gas to a high value.
To attain the object, the present invention provides a method for drying wood comprising the steps of putting wood fuels such as waste wood into a combustion chamber provided in a lower area of a combustion gas generating furnace, burning the same, and introducing a high-temperature combustion gas generated by the burning into an upper area of a drying room housing green wood, to thereby thermally dry said wood by said combustion gas, wherein the thermal drying of said wood is carried out by maintaining concentration of said combustion gas contained in said drying room atmosphere existing in said drying wood to a high value. The method is further characterized in that the maintenance of the concentration of said combustion gas is carried out by controlling the discharge amount of the drying room atmosphere discharged from the chimney and the introduction amount of the combustion gas introduced into the drying room. The method is furthermore characterized in that the maintenance of the concentration of said combustion gas is carried out by controlling the recovery amount of the drying room atmosphere recovered from the drying room into the combustion chamber and the introduction amount of the combustion gas introduced into the drying room. The method is furthermore characterized in that the concentration of said combustion gas is maintained to a high concentration in the range of 60 to 95 (volume) %. The method is furthermore characterized in that the pressure of a drying room atmosphere is maintained to a high value by hermetically sealing said drying room. The method is furthermore characterized in that said pressure of a drying room atmosphere is maintained to a high pressure in the range of 1.5 to 5 atmospheric pressure. The method is furthermore characterized in that the superheated steam is generated in said combustion gas generating furnace and introduced into the drying room together with the combustion gas.